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48 hour Trajectory Forecast for high GASP aerosol optical depth, ta ≥ 0.4

Sample Trajectory Forecast GASP AOD image

Sample Trajectory Forecast for high GASP ta plot

The trajectory forecast animation plots the initial GASP (GOES Aerosol/Smoke Product) aerosol optical depth (in color contours), GOES channel 1 reflectance (in gray contours), an animated ~48 hour air parcel trajectory forecast (in magenta-white colors), and the 3hr accumulated precipitation (in yellow). The trajectory forecasts are initialized at 15Z, 18Z, and 21Z every day.

GASP aerosol optical depth, ta

The GASP ta used for these plots is based on the GOES Aerosol/Smoke Product (Knapp et al., 2002; Prados et al.,2007), which is derived from the visible channel of GOES-12 imager. The retrieval algorithm runs near-real time with 30-minute interval during sun-lit time and 4x4 km^2 spatial resolution at NOAA/NESDIS. The retrieved AOD is plotted on a scale of 0.0 to 1.0 with ta > 1.0 shown as dark red.

Forward air parcel trajectory forecast

Sample Trajectory Forecast GASP AOD > 0.4 image

Sample plot with locations of high ta (> 0.4) used to initialize forecast trajectories

This plot shows the locations where high values of GASP ta (>0.4) are located and used to initialize starting locations for forecast trajectories. The high GASP ta values are determined by calculating mean ta values on a 50 km x 50 km grid, or 5 pixels square.

The trajectories are initialized at the high ta values at 50mb, 100mb, 150mb, and 200 mb above the surface level, with a maximum number of 100 trajectories. The initialization points for the trajectories are colored to the AOD scale and the GASP data close to the initial time remains on the plot. The air parcel trajectories are run using the 12Z NOAA (National Oceanic and Atmospheric Administration) /NCEP(National Center for Environmental Prediction) NAM (North American Mesoscale Model) forecast data providing a ~48hr forecast via trajectories. The pressure levels of the trajectories are plotted in mb and colored to a magenta-white scale. The 48-hour forward trajectories are plotted at each frame of the animation. The 850mb wind field vectors are plotted to show wind direction and speed.

The forecast trajectory animation details the potential vertical movement of high aerosol loads in the troposphere. The darker colors on trajectory pressure scale are limited to the 1000-800 mb pressure levels to help distinguish trajectories moving within the boundary layer. As the forecast trajectories progress in time, darker color trajectories indicate a flow of air towards the surface, and a potential similar movement of the aerosols, captured by the high ta. White color trajectories indicate a upward movement in the air flow.

GOES channel 1 reflectance and 3hr accumulated precipitation

The GASP cloud mask is derived from infrared channels 2 and 4 radiances. A ta is not derived for cloud filled pixels, therefore the clouds fields are represented by the channel 1 reflectance to help define synoptic weather features important to the movement of aerosols.

The 3 hour accumulated precipitation used for these plots is from the NAM forecast model (NOAA/NCEP). Areas where 3 hour accumulated precipitation is greater than 2kg/m2 are shaded yellow and can be used to determine “rain out” or potential for wet deposition in areas of high aerosol loading.

Acknowledgements:
GASP data is being obtained from NOAA/NESDIS/Office of Research and Applications.

NAM meteorological forecast data is being obtain from the National Weather Service component of NOAA

References
Knapp, K.R., T.H. Vonder Haar, and Y.J.Kaufman (2002), Aerosol optical depth retrieval from GOES-8: Uncertainty study and retrieval validation over South America, J.Geophys. Res., 107(D7), 4055, doi:10.1029/2001JD00505.
Prados, A.I., S. Kondragunta, P. Ciren, and K.R.Knapp (2007), GOES Aerosol/Smoke Product (GASP) over North America: Comparisons to AERONET and MODIS observations, J. Geophys. Res., 112, D15201, doi:10.1029/2006JD007968.

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